Laser Welding Titanium and Titanium Alloys

Friday, May 8th, 2009 at
5:49 pm

Laser welding titanium is an excellent process for welding titanium and certain titanium alloys. Since titanium is an extremely light metal with a very high strength, it’s often utilized in many different sectors such as the aerospace, medical, and chemical industries. It’s so strong, in fact, that titanium has a strength to weight ratio that’s higher than any other metal. It’s strength approaches that of steel, with a weight savings of 45%.

Because of its excellent corrosion resistance, it is particularly well suited for use in the chemical and petrochemical industries, owing to their typically harsh operating environments.

The first step you need to take before you laser weld titanium, is to verify that the materials are weldable. Pure titanium, and most of the alpha alloys are either easily welded, or at the least weldable.

Once you’ve verified that the titanium, or titanium alloy you’re using is weldable, you’ll need to thoroughly clean them. Much like most metals, cleaning titanium before welding is of the utmost importance. Any fingerprints, grease, dirt, oil, paint, or any other foreign substance must be removed prior to welding. This must be done with a solvent that is approved for use with titanium. Under no circumstances should water be used to rinse any titanium parts. Failure to do so could cause stress corrosion cracking when the metal is heated during the welding or heat treating processes. Hydrogen in a cleaning solution will cause embrittlement and should be avoided.

A proper joint is also a very important consideration when laser welding titanium. Since there is no filler metal added when using the laser welding process, square butt joints or lap joints are the typical joint configuration.

Due to the fact that titanium is very reactive with nitrogen and oxygen, almost all welding processes require a trailing shield. Laser welding is no different. This shield needs to be large enough to allow the welded joint to cool to below 800 F, or 425 C. The type of shielding gas used is argon, helium, or a mixture of the two of them.

The shielding gas needs to be extremely dry, as any moisture in it can be harmful to the weld. As a rough measure, it’s possible to get an idea of the contamination of the shielding gas by the color of the weld after it cools. A white flaky coating means it was very contaminated and the weld may not be acceptable. A blue color indicates moderate contamination, but often the weld will still be acceptable. A very light bronze indicates that the gas was relatively pure and there is only a small amount of contamination on the surface.

A few of the benefits of laser beam welding titanium include the fact that the whole process is very easily automated. This in turn leads to a high repeatability factor. There’s also no need to buy expensive filler wire. Since the weld zone and laser power are tightly regulated, there is much less chance for the welded parts to distort from excess heat input.

So as you can see, there are a myriad of reasons why laser welding titanium may be the right choice for your application. Obviously, due to the high initial equipment expense, it’s not for all applications. But if you’re looking for a weld of high quality and repeatability for use in a production environment, laser welding titanium may be your best choice.